SPECIFICATIONS FOR NONBITUMINOUS EGAD MATERIALS. 3 



a means toward standardizing not only specifications for broken stone 

 but also plant practice in the production of broken stone for highway 

 work. 



The forms of specification adopted for broken stone as well as other 

 nonbituminous road materials are, in general, those recommended 

 by the First Conference of State Highway Testing Engineers and 

 Chemists.^ Following each specification is a brief descriptive para- 

 graph, stating the general conditions governing its uses and what 

 modifications may in certain instances be made. More detailed in- 

 formation and advice relative to methods of construction may be 

 obtained upon application to the Bureau of Public Roads. 



It is realized that all classes and types of nonbituminous road ma- 

 terials have not been covered, and it is intended to add to the num- 

 ber of these specifications from time to time. For the convenience of 

 engineers, and in order to make this bulletin complete in itself, the 

 methods of test to which reference is made in the specifications, and 

 directions for sampling, are given in an appendix. 



Table I. — Relation of commercial revolving screens to laboratory screen 

 requirements for broken stone. 



Type of road. 



Revolving screens. 



3-inch. 2-incli. 1-inch. §-inch. J-inch 



Per cent passing laboratory screen of 

 same size. 



Water-bound: 

 Bottom course. 



Top course 



Screenings 



95+ 



Base or both courses 



Screenings 



Cover for bituminous surface treatment : 

 Coarse chips 



95+ 



Fine chips 



Bituminous macadam: 



Bottom course 



Top course 



Chips 



Screenings 



Bituminous macadam: 



Wearing course 



Chips 



Bituminous concrete: 



One-size stone 



Chips 



Graded bituminous concrete: 



Coarse aggregate 



Chips 



Bituminous concrete (Topeka): 



Broken stone 



Sheet asphalt: 



Binder stone 



Cement concrete pavement: 



Coarse aggregate 



Cement concrete base: 



Coarse aggregate 



95+ 



95+ 



15- 



95+ 



15- 



95+ 



95+ 



95+ 



15- 

 95+ 



15- 



95+ 



95+ 



15- 

 95+ 

 95+ 



15- 

 95+ 



95+ 



95+ 



95+ 



85+ 



95+ 



95+ 

 95+ 



40-80 



40-80 

 15- 

 15- 



15- 

 40-80 



80- 



* U. S. Department of Agriculture Bulletin 555. 



